The use of Internet Protocol (IP)—based networks to transmit data, such as electronic mail (e-mail), facsimiles (e-faxes) and voice communication, is becoming increasingly prevalent. With respect to voice communication in particular, voice over Internet Protocol (VoIP) allows voice communication to be sent over IP-based networks by digitizing voice data into packets and then sending them using IP-based routing. In this regard, VoIP communication can be thought of as the digital counterpart to traditional switch-based communication services, such as the public switched telephone network (PSTN). VoIP communication is rapidly gaining acceptance over traditional switch-based communication services for several reasons. For instance, unlike traditional switch-based communication, VoIP does not require a complex switching infrastructure and is therefore considerably less expensive to implement. Furthermore, VoIP allows a single network to carry both voice and data, which can be financially beneficial to users having existing underutilized network capacity. For individuals, VoIP provides extremely low cost calling rates for services such as long distance calling. For enterprises, VoIP provides new functionality, especially when integrated with wireless fidelity (Wi-Fi) networks. This includes improved caller routing/tracking and integration with services such as addressing, in-call file exchanging, video conferencing and call logging.
In addition, mobile devices that combine mobile computing functionality with mobile phone functionality, such as smartphones, personal digital assistant (PDA) phones and the like, are also becoming increasingly popular. These devices typically implement a full-featured compact operating system, such as Windows CE®, Palm OS®, or Symbian OS®, and are usually equipped with multiple wireless network interfaces—including a cellular interface (provided by a cellular radio on the device) and wireless fidelity (Wi-Fi) interface (provided by a Wi-Fi radio on the device).
As mobile devices become ubiquitous, they are increasingly being used to send and receive data via their cellular and Wi-Fi interfaces. In this regard, Wi-Fi interfaces offer several advantages over cellular interfaces with respect to communication over IP-based networks. For instance, with real-time applications such as VoIP, jitter and loss rate are higher on cellular interfaces than Wi-Fi interfaces. Furthermore, when engaged in data transmission, Wi-Fi radios on mobile devices are more energy efficient than cellular data radios. In other words, cellular interfaces on mobile computing devices consume more power when transmitting data than Wi-Fi interfaces do. This is important because mobile devices typically rely on batteries as their main source of power.
There are other reasons why Wi-Fi interfaces are advantageous for IP-based communication. For instance, cellular network providers usually require that a user purchase a cellular data plan, which is typically expensive, in order to use the cellular network for data transmission. For certain real-time applications such as VoIP that produce significant network traffic, cellular network providers usually require an even more costly unlimited cellular data plan.
One disadvantage of using Wi-Fi interfaces, however, at least on mobile devices, is that such interfaces can be costly in terms of power usage (and thus battery life) to keep idle (connected to a network but not engaged in data transmission). This is because Wi-Fi interfaces continually scan for wireless network activity, even when they are idle. Therefore, from an energy consumption perspective, the battery life (between charges) of a mobile device is significantly reduced when its Wi-Fi interface is enabled (Wi-Fi radio powered on). This can make it impractical to use Wi-Fi interfaces for certain real-time applications, such as VoIP, which require an interface to remain enabled and idle in case transmitted data is sent to the mobile device.
Accordingly, there is a need to minimize the energy consumption of a Wi-Fi interface on a mobile device running real-time applications, such as VoIP, e-mail or instant messenger, while still allowing for the advantages associated with using the Wi-Fi interface to be leveraged.